Measurement of Neutron Capture Cross Sections with Fe-Filtered Beam

The neutron capture cross sections of 93 Nb, 115 In, 127 I, 165 Ho, 181 Ta, 232 Th and 238 U were measured using the Fe-filtered beam. A 15-cm thick Fe filter was placed in the neutron beam produced by the KUR 46-MeV electron Linac and capture prays were detected by two C 6 F 6 scintillation detectors located at an 11.7 m-flight path. The pulse-height weighting technique was used to determine the relative capture pray detection efficiency. The neutron flux was measured by the same detectors, whose detection efficiency for the 480-keV pray from the 10 B(n, α 1 ) reaction was calibrated by the saturated resonance capture in Ag at 5.2-eV. Self-shielding and multiple scattering corrections were applied to the data. The results of 24-keV capture cross sections are 340, 770, 780, 1,280, 880, 520 and 520 mb for 93 Nb, 115 In, 127 I, 165 Ho, 181 Ta, 232 Th and 238 U, respectively. Total errors are 5 to 8%, with an estimated systematic error of 4%. The discrepancy between the present results and other data measured recently is within 10%.